Category Archives: EuroSun2008-4

The Solar XXI PV systems

1.1 PV Facade

The PV facade has 76 multicrystalline silicon modules BP3160, with a total peak power of 12,16 kW and an area of 95,6 m2.

The direct current (d. c.) produced by the PV generator will be converted to alternate current (a. c.) with three inverters Fronius IG 40. Each inverter have a nominal power of 3,5 kW, a maximum efficiency of 94,5 % and an European efficiency of 93,5 %.

Table 1. Facade — PV Modules configuration

Inverter

Modules

Nr. of

Peak power

/ string

strings

(W)

1- Fronius IG 40

7

4

4 480

2- Fronius IG 40

8

3

3 840

3- Fronius IG 40

8

3

3 840

Total

12 160

image407

Fig. 2. PV Facade system configuration.

Windows and solar gains

Windows have a much higher U-value than the opaque envelope and are therefore likely to account for high heat losses/gains. Conversely, its transmittance allows solar gains to enter the building, contributing to the heating loads in the cold periods. High levels of insulation can be achieved with several numbers of panes, low emissive coatings and gas filled cavities, or with new materials such as the aerogel. During the night period, when temperatures drop, the use of movable insulating systems prevents further heat losses. Over the summer, solar gains should be avoided. Passive solutions may include overhangs, reveals, movable shutters or blinds.

The quantity of radiation incident on the facade varies with the time and day of the year. Designing for solar gains strongly depend on the orientation, site layout and sunlight availability.

3.5 Passive cooling

There are a number of different approaches to passive cooling design. They may involve buoyancy and cross ventilation, night ventilation usually associated with strong inertia, ground cooling, evaporative cooling and night sky radiation.

Throughout Europe, a relatively large diurnal swing in air temperature creates the possibility of night time ventilation to cool the building’s heat storage capacity, delaying its release to the space, as well as reducing temperature fluctuations. The ground below 3-4 meters has a relatively stable temperature which may be used to cool or pre-heat the air or a fluid passing through buried pipes. Its strong inertia may also be used for heat storage.

Although night sky radiation can promote cooling of the roof surface, this is rarely used in cities due to the pollution and the greenhouse effect which significantly reduces the radiation exchange to the atmosphere. Conversely, evaporative cooling is commonly found in traditional architecture, particularly in dry and hot climates of southern Europe. Some strategies of indirect evaporation allow its use in more humid climates.

PV Electrical Performance

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image488

Fig. 3 presents the PV cells temperature for the three configurations studied for a sunny winter and summer day in Yellowknife with leeward wind. As it can be observed, the PV cells temperature in configuration A and B are very close since the PV laminate replaces the outer pane in both cases. For the winter day, the maximum PV cells temperature difference between configuration C and configuration A or B is of approximately 12oC during daytime. For the summer day, this difference is of about 16oC. The DC electrical power produced by the PV cells for these 2 days is presented in Fig. 4. The graphs reveal that the power generated by configurations A and B is very similar, but at peak sunshine hour, approximately 14% and 20% greater than configuration C for the winter and summer day, respectively. This can be explained by the higher cells temperature and the fact that less radiation strikes the PV cells in this configuration because of the outer glazing layer reflecting and absorbing part of the incident solar radiation.

Подпись: (a) image490
image491

Fig. 3. PV cells temperature for a winter day (a) and a summer day (b) in Yellowknife.

Fig. 4. DC electrical power for a winter day (a) and a summer day (b) in Yellowknife.

BIPV in New York City

New York City is experiencing an unprecedented construction boom. With additional projects in the pipeline — such as the rebuilding of the World Trade Center site and various other major projects underway throughout NYC — this is a unique time to look at how the use of Building Integrated Photovoltaic (BIPV) systems may have an impact on the City’s future skyline. One of the main drivers attributed to the growing interest in BIPV systems is NYC’s challenge to meet growing peak electricity requirements. NYC is an electric ‘loadpocket’. It is geographically isolated — consisting of 3 islands and a peninsula — yet it has a peak demand of well over 10,000 MW. To maintain voltage support and reliability standards, the New York Independent System Operator (NYISO), which manages NY State’s bulk power transmission system and wholesale power markets, has determined that NYC must be capable of generating 80% of its peak electric power requirements within the 5 boroughs that make up the city. However, power plant siting has generally become more difficult and this is especially true in NYC, where real estate options are constrained, real estate values are high and community values overlap. [2]” In addition to the challenge of power supply,

[3] Introduction

An interactive wall is a building’s external wall, which reacts to weather conditions and transforms them according to user’s requirements. It is an important element of the indoor environment’s control system and, in consequence, for energy management of the whole building. The inputs of the interactive wall system include weather parameters, independent of human will and impossible to predict in the long term. Outputs include parameters of the indoor environment. They vary for different kinds of human activity and change during the whole day or over different seasons. Both the inputs and the outputs of the system are changeable, although in different ways. The understanding of this model is necessary to realize that the interactive wall system is very complicated and difficult to implement in practice.

[4] Natural ventilation

The Evaluation Process

1.1. Initial evaluation

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For a systematic process of evaluation a flow chart (see Figure 1) has been developed showing the logical sequence of worksteps to be carried out.

Подпись: improvements possible? results

image373 Подпись: list of remarks Подпись: exclusion

ok?

Подпись: results ok? ^Jistof risks^)

recommendations

Fig. 1. Flowchart for the evaluation system

At first boundary conditions and minimum requirements (ko-criteria) are defined. Building type, location and especially the type of use were among the various criteria to be considered for the fa? ade.

The facades to be evaluated are classified by means of a “morphological box” for variations of design parameters such as shape, orientation of windows, construction, material, properties of opaque and transparent building elements, ventilation as well as cleaning and maintenance. In total, the “morphological box” has 23 fa? ade parameters, each of which has up to six variation steps.

Following the flowchart, an initial evaluation test has to be carried out to determine whether the fa? ade under consideration fulfills the compulsary minmum requirements. A list of possible problems can be made. If all boundary conditions and ko-criteria are fulfilled, then the more detailed evaluation can start. If otherwise, the fa? ade under consideration does not meet the first conditions, even with some possible improvements, then it will be taken out of the evaluation system.

Inclusion of solar thermal collectors

The previous section has shown that it is possible to comply with the energy requirements of the RCCTE even without solar thermal collectors for domestic water heating. Yet, two important questions remain.

One is whether the use of solar thermal collectors, mandatory by the RCCTE, can be discarded for historical areas based on a criteria of “justified esthetical incompatibility”. According to the law, it is up to the licensing authorities (generally the municipalities) to judge this justification. The authors will take no definitive position here, although they admit that in some cases the relief from compliance may be justified.

The second question is, regardless of the answer to the previous paragraph, what is the energy relevance of the collectors if they are indeed applied, and its consequences in terms of energetic classification — especially its relevance to achieve class A+. This assessment was made by analysing a case with the same envelope and constructive solutions of table 8, but now adding solar collectors of medium performance (n0=0.73; ai=5.0 W/m2K; a2=0.05 W/m2K) for heating of the domestic hot water, maintaining the gas boiler as auxiliary system. As prescribed by the regulation a collector area of at least 1 m2 per person was considered. Table 9 shows the results of this exercise, which shows that by adding the solar thermal collectors the buildings now fall within class A. This strong effect is easily understood if we recall eq. 1 which shows that the primary energy consumption Ntc strongly values the energy consumption for domestic hot water when compared with the consumption for heating and for cooling.

4. Conclusions

Portuguese thermal regulation for residential buildings, the RCCTE is applicable to all new or significantly retrofitted buildings. It foresees the possibility that for buildings in historical areas certain requirements of the regulation may be discarded if an incompatibility with the architectural

frame are found and duly justified. An analysis to 6 apartments undergoing a retrofitting process in the downtown area of Porto (the “Ribeira”- classified by UNESCO as human heritage patrimony) allowed the identification of some important findings.

Table 9: Energy indexes after the upgrade to ensure compliance + average solar collectors

Apartment 1

Apartment 2

Apartment 3

Apartment 4

Apartment 5

Apartment 6

Collector area (m2)

2

2

2

1

3

1

Nic/Ni

100 %

82 %

99 %

68 %

95 %

78 %

Nvc/Nv

28 %

58 %

42 %

71 %

18 %

28 %

Nac/Na

58 %

58 %

58 %

58 %

72 %

58 %

Ntc/Nt

44 %

42 %

45 %

41 %

52 %

42 %

Label

A

A

A

A

B

A

The first major finding was of a process nature and showed a possible trend towards trying to exempt the buildings from compliance with the RCCTE even before making any calculation and therefore without proving any incompatibility. The licensing authorities (generally the municipalities) and ADENE shall thus pay particular attention to this point in order to ensure proper compliance and ultimately a better energy performance of their built environment, with the known benefits in terms of comfort, economy and environment.

The second major finding was that, even if the requirement of installing solar collectors is hypothetically discarded, it is possible to comply with the energy requirements of the regulation (Nic, Nvc, Nac and Ntc) without interfering with the appearance of the buildings. The major features to take into account for seem to be:

• — The use of about 3 to 8 cm of thermal insulation (depends of the specific case) at an internal position relatively to the traditional stone walls. More than complying with the direct minimum requirements, this is needed to ensure compliance with the maximum heating needs.

• — Avoidance of an internal envelope using extensively thick gypsum layers as internal finishing, since it may lead to low thermal inertia. This is because the solar factors of traditional internal shading devices are compatible with medium or high thermal inertia but not with low inertia ones.

The third major finding was that, despite the fact that being at an historical area may in some cases be a justified reason to discard the installation of thermal solar collectors for water heating; its installation seems to be crucial to achieve buildings with energy class A.

5. References

[1] AdePorto — Energy Agency of Porto: Energy Matrix of Porto, Porto, 2008 (in Portuguese).

[2 ] INE — Institute Nacional de Estatistica, www. ine. pt [3 ] www. portovivosru. pt/

[4 www. adeporto. eu/

[5 DL80/2006 de 4 de Abril de 2006 — RCCTE — Regulamento das Caracteristicas de Comportamento Termico dos Edificios

[6] European Comission: 2002/91/EC — Energy Performance of Buildings Directive,

Acknowldegments

The authors thank the cooperation of Porto Vivo SRU, in the person of Eng. Antonio Baptista, and of SOPSEC S. A., in the person of Eng. Pedro Pinto, which provided free access to the retrofitting design data for the analysed buildings, as well as to AdEPorto for the financial support to the internship of Eng. Francisco Craveiro.

Product benchmarking

In the D4S approach, generic strategies and guidelines are recommended to create more sustainable products [3]. Within the Delft program, this approach is now being further elaborated and scientifically grounded with respect to the modelling of the specific group of PV powered consumer products. Therefore, no specific design guidelines could be applied by the young designers involved in this project. However, in the application of D4S in almost 20 years of ecodesign of industrial products, the most significant guideline undoubtedly has been the advice to use ecobenchmarking as much as possible as one of the most powerful design tools.

In the D4S approach, benchmarking is defined as follows: “Benchmarking is the process of improving the performance of an existing product by continuously identifying, understanding, and adapting outstanding practices and processes found both within and outside of the organisation. Benchmarking is a structured approach to compare the environmental performance of a company’s products against competitors’ products and to generate improvement options” [3]. In the D4S manual and the book ‘Adventures in EcoDesign of Electronic Products’ [4] specific guidelines and a stepwise planning of ecobenchmarking have been described.

The phase model of Buijs & Valkenburg [1] also indicates the importance of creating an inventory of similar products to improve a specific product design.

Final considerations

With this experience, we aimed to offer a methodological proposal and a set of architectural and technological tools easily applied and appropriated for the improvement of the popular rural habitat of Chubut, Argentina. It has also served to make it possible for the inhabitants to discern about their expectations and skills and to achieve the production of their habitat by means of assisted self­management. That was done by taking advantage of their contexts — natural and cultural — and in order to reconquer people’s dignity through their own effort and mutual help to achieve a sustained local development.

5. Bibliography

• Garzon, B. Arquitectura Bioclimatica. Arquitectura Bioclimatica. NOBUKO. ISBN 978-987­584-096-6. Buenos Aires, Argentina. 2007.

• Garzon, B. Variables Bioclimaticas y uso de la Energia en Viviendas Espontaneas y Oficiales de Interes Social: Analisis y Propuestas. Pags. 113-130. 2005. Red CyTeD. ISBN 972-676-200-6. Editor: Helder Goncalvez, INETI. Lisboa, Portugal.

• Mele, E.; De Benito, L.; Garzon, B.; Piva, R. Rural Bioclimatic Houses Built by the State in Chubut. World Renewable Energy Congress-IX. Pags. 1-6. Florencia, Italia. ABITA Interuniversity Research Center, University of Florence — WREC. Brighton, UK. Agosto, 2006.

• Mele, E.; De Benito, L.; Garzon, B. Coccion y homeado solar en viviendas de interes social desde el estado en Chubut, Argentina. Estudios de Arquitectura Bioclimatica. Anuario 2006. Vol. VIII. Editorial LIMUSA. Pags. 121-130ISBN-13: 978-968-18-6816-8. Mexico D. F. 2006.

• Garzon, B. Los Cerramientos en Tierra y su Eficiencia Economico-Tecnologico-Termico — Energetica en Tucuman, Argentina. Revista Energia y Desarrollo E&D N° 28. Dep. Leg. 2-3­754-98. Pags.2-8.CINER. Cochamba, Bolivia. Mayo, 2006.

Building energy demand

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The specific heating demand of the investigated building was determined to be 12.3 kWh/m2a. This value proves the building to be designed according to passive house standard. Due to high internal loads and large glazing areas, a cooling demand was expected even for a location in central Germany. However, due to the external shading devices used, the simulated cooling demand of the whole building (not considering the server room) was determined to be 1.9 kWh/m2a. In opposite to this relatively low average value over the year, the maximum cooling load of the building was determined to be larger than 30 kW at peak times.

Fig. 3: Energy balance of the building (without server room).

Winter measurements

Concerning the external conditions the monitoring periods that presented lower temperatures during more time were the ones corresponding to the measurements made in housing units1a, 2, 4,

5 and 9, during approximately 5% of the time the temperatures were below 5°C and in approximately 30%-40% of the time the temperatures were between 5°C and 10°C. The other periods had temperatures between 5°C and 10°C approximately 20%-25% of the time.

All the different monitoring, the exterior temperature was most of the time between 10°C and 15°C, near or than 50% of the time. The corresponding measurement periods in the housing units 7, 8, 10 and 11 were the ones to show temperatures between 10°C and 15°C during comparatively more time than the others, approximately 65% of the time. For the different monitoring periods the temperature was between 15°C and 20°C in approximately 10%-20% of the time. Only the measurements in housing units1b, 8 and 11b resulted in exterior temperatures between 20°C and 25°C.

None of the compartments monitored during the 2007-2008 winter months presented interior temperatures below 15°C. However, some had temperatures below 18°C. The only apartment with glazing areas practically to the south that had temperatures below 18°C was dwelling 9 (7%-20% of the time), because it was closed and unoccupied during some time (windows closed and blinds lowered). The other housing units that had temperatures below 18°C were dwelling 8 (west) in 16%-26%of the time, and dwelling 5 (east) in 0,5%-4% of the time.

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The compartments of the housing units with glazing areas oriented practically west and east were the ones that presented interior temperatures between 18°Cand 20°C during more time, approximately between 55% and 70% of the time. Only some compartments with glazing areas practically to the south presented temperatures between 18°C and 20°C, these were housing unitsla, 3, 9 and 11a, in 6% to 26% of the time. The compartment of dwelling 1 with glassed area to the north, presented temperatures between 18°C and 20°C in 32%-52% of the time.

image437

It was the dwellings with glazing areas oriented to the south, SSE and SSW that presented the temperatures between 20°C and 25°C for more time, on the average 85% of time; while the west presented between 4% and 45% of the time. In some compartments with glazing areas practically to the south (S, SSE, SSW) temperatures above 25°C were obtained even in the cold season; these were housing units: 1 (11%-14% of the time), 2 (10%-27% of the time), 4 and 11 (1-1,5% of the time).

Mean of the mean temperatures: The average of the exterior average temperatures was 11,5°C during the different monitoring periods, while the average of the interior average temperatures in the different monitored compartments was approximately 21°C. For the compartments with glazing areas practically to the south, the average of the average temperatures was approximately 22°C, while for the compartments with glazing areas practically to the east and west was approximately 19,8°C.

Mean of the maximum temperatures: The average of the maximum exterior temperatures was approximately 15°C during the different monitoring periods. For the compartments with glazing areas practically to the south the average of the maximum temperatures was approximately 23°C, being that for dwelling 1 was approximately 25°C and for dwelling 2 25°C-27°C. Some housing units presented an average of the maximum temperature below or very close to 20°C, these were mainly the compartments with glazing areas oriented to the west, east and north. In dwelling 1, while a living room compartment (facade S +E) presented an average of the maximum temperature

of 25°C, the bedroom (facade north) presented an average of 20°C. When comparing dwelling 2 with 5 (similar exterior conditions and average of the maximum temperatures), dwelling 2 presented an average of the maximum temperatures higher than dwelling 5 of 4°C -5°C.

Подпись: Fig.11. Thermal amplitude for the different compartments - winter 2007-2008.

Mean of the minimum temperatures: The average of the exterior minimum temperatures was 8-9°C in the different monitoring periods. Most of the studied compartments with glazing areas practically to the south presented an average of the minimum temperatures greater than 20°C (in general close to 21°C), the west and east housing units had averages lower than 19°C. In dwelling 1, the living room had an average of the minimum temperature of 22°C, while the bedroom 19,7°C.

The exterior thermal amplitude practically varied between 13°C and 18°C in the different monitoring periods. The largest interior thermal amplitude was obtained in the measurements performed in housing units 8 and 11, while the lowest was obtained during the measurements in dwelling 7. The largest interior thermal amplitudes were obtained during the measurements in the compartments with glazing areas oriented practically to the south, amplitudes varying between 5°C and 11°C. Only dwelling 4 had amplitude of 2,5°C, and this due to a heating system type (programmed to maintain temperature of 22 ° C). In the remaining monitored compartments (with glazing areas practically to the east, west and north) the thermal amplitudes were between 3°C e 4,5°C.

3. Conclusions

This paper shows the results obtained in a group of building apartments block during a monitoring campaign (2007-2008), in summer and winter, in order to study the internal thermal comfort in building with similar characteristics (high percentage of glazing area 75% of facade area), that have been recently built in Lisbon. The results shows for summer period that all dwellings presented mean temperature above 25°C, close to 80% — 90% of the time the housing units that have large south facing glazing areas reached temperatures above 27°C. In winter monitoring period the registered mean temperatures was 21°C. It was also verified that: the apartments with large south facing glazing areas has temperatures above 23°C, and on certain occasions even reach 28°C. The fractions with large east and west facing glazing areas showed mean temperatures normally between 19°C and 21°C (the minimum temperature observed was equal to 17°C). These very high temperature values in winter can be explained by the existence large glazing areas and the adaptation of high insulated levels for the opaque envelope. With the inquiry distributed among the occupants it was possible to confirm that the conventional heating systems were switched on often. The results shows also that in most of the apartments are uncomfortable conditions in both summer and winter seasons if for comfort temperature are considered 25°C and 20°C, respectively. In these kinds of buildings it is necessary to take much care with the glazing areas and solar protection. The relative humidity was normally between 35% and 65% in the monitored housing units for both seasons.

— Portugal /

References

H. Gonsalves, M. Panao, S. Camelo, A. Ramalho, J. M. Graga, R. Aguiar, (2004). Ambiente Construido, Clima Urbano, Utilizagao racional de energia nos Edificios da Cidade de Lisboa, Lisbon.

H. Gongalves, A. Ramalho, R. Silva, C. Rodrigues, (2006). Comportamento Termico do Edificio Solar XXI — Primeiros Resultados, Lisbon.

H. Gongalves, A. Ramalho, (2006). Comportamento Termico de uma Vivenda Solar Passiva — Casas em Janas Sintra, Lisbon.